Thursday, March 22, 2012

You know springtime is upon us when Varied Thrushes and Dark-eyed Juncos insist on waking you up at the crack of dawn with their incessant singing! Indeed, in the past few weeks, all manner of avian-related noise in my backyard has increased two- or threefold. Most of my feeder-frequenters have "changed their tunes," so to speak, from typical calls to territorial songs, making my neighborhood a much more melodious place.

Now, in case you were unaware, in the world of ornithology bird noises are classified into three groups: calls, songs, and mechanical sounds. A proper discussion of mechanical sounds would require an entire blog entry all on its own, so we'll hold off on that until a later date. For now, I hope you can be content with simply knowing that a mechanical sound is any non-vocal sound produced by a bird (such as bill clacking in ravens, drumming in woodpeckers, and the recently famous tail-squeak of Anna's Hummingbirds). For those of our dear readers with an insatiable and demmanding appetite for more knowledge, I shall leave you in the capable hands of your Google search bar (search for Chris Clark's research on tail sounds in Anna's Hummingbirds).

For the rest of us who haven't been sidetracked by mechanical sounds, I'll go ahead and get back to the calls and songs. What's the difference between these two types of vocalizations? In some species, the differences can be quite difficult to make out, but for others - most songbirds for example - they are as different as night and day - or perhaps, summer and winter? In general, most songs tend to be more elaborate, longer, and change with the seasons, while calls tend to be short and simple. As with most broad generalizations, there often appear to be more exceptions to the rule than conformists. Let's stick to the conformists for now.

A Dark-eyed Junco sings from his perch. Listen below.

Warblers, wrens, kinglets, and most sparrows tend to conform very nicely to these generalizations regarding songs and calls. Take the vocalizations of the Pacific Wren for example. Their calls are very short, simple and repeated, while their songs are quite complex and can continue for up to 120 seconds (one of the longest wren songs ever recorded).

So what's the purpose of all this singing? The answer, as it often does in the natural world, brings us back to reproduction. Bird vocalizations are better defined as songs when we learn why they are produced. Singing behavior is a product of changes in hormone concentrations due to the lengthening of days. As days get longer in the spring, and the breeding season draws ever closer, the production of sex-related hormones (such as testosterone) spikes, and male songbirds begin singing their heads off every morning on your windowsill.

Calls, on the other hand, are not generally regulated by hormones. Instead they are communication- and coordination-related. Warning calls, contact calls, flight calls, foraging calls, distress calls, alarm calls - all of these sounds are produced for the coordination of behaviors. An alarm call will alert other birds in a flock to a predator. Flight, contact, and foraging calls help birds keep track of one another while moving in flocks (Bushtits for example). Distress calls can coordinate mobbing behavior, deterring predators. In fact, Black-capped Chickadees have been known to mimic the distress calls of other species, inciting more birds to join an anti-predator mob.

The diversity and repertoires of bird songs and calls is utterly astounding. Every year I hear chickadees, Steller's Jays, Bewick's Wrens and juncos make sounds I have never heard them produce before. I often feel like keeping up with new birdsongs is like trying to keep track of top-40 pop music! For a nice example of how songs can vary within a species, check out the "typical" Ruby-crowned Kinglet songs below.

Learning bird songs is a rewarding and enlightening experience. I have provided a few common songs and calls here to get you started. If you would like to continue your listening lessons, try looking up common bird songs on Xeno-Canto or in the Macaulay Library of Animal Sounds.

Also, it is interesting to note that exactly one year ago today, Dennis Paulson wrote a similarly themed blog entry about the arrival of spring and birds singing and breeding! Funny how the timing of this worked out! Check out last year's blog entry here.

- Robert Niese
Education and Outreach Coordinator

Bushtits use a variety of contact calls to keep track of oneanother while foraging in large flocks. Listen to these calls below.

Song Sparrow songs are also quite common in my neck of
the woods. But don't get me started on song-variation in
sparrows. That's a topic for another day. Or week, perhaps.
Here's a typical song for Pacific Northwest Song Sparrows:

And here's a very nice recording of their alarm calls:

In my opinion, Ruby-crowned Kinglets sing one of the oddestsongs in Washington! Each song consists of three parts and each of those parts varies greatly between individuals.Here is a "typical" song for a "Northwestern" Ruby-crowned Kinglet. Note the three parts. The high-pitchedsection, the descending twitter, and the see-sawing warble:

Now listen to how this individual from the Rockies changes hissong. It's different but we can still pick-out the three main parts:

Some birds will rearrange parts of their song, like this one from Quebec:

And then there are oddballs, like this population in British Colombia:

American Robins have remarkably diverse vocalizations.Here is a typical Robin song:

Thaxter's writing about the poem makes it clear that its source was an encounter with a plover near its nest, but her description makes it sound as if she was watching a Sanderling (Calidris alba), the most common sandpiper on open ocean beaches almost anywhere in the world. Had it been a Sanderling, she would have marveled at its hyperactivity as it charged the ocean waves and then retreated as the waves charged back.

Sanderlings are particularly common on the Pacific Northwest coast, where the richness of the ocean waters enhances the productivity of the intertidal zone. The only higher densities recorded for the species in the Americas in winter are along the Humboldt Current beaches of Peru and Chile. Flocks of hundreds of birds occur all along our outer beaches, and they are tame enough (and presumably used to crowds of people) that you can watch their foraging behavior at great length.

Sanderlings dash in and out of the waves to get prey exposed by the receding water, but they also spend much time above the waves running around on either dry or wet sand. Like many other sandpipers, they can find their prey either visually or tactilely.

Tactile foraging involves plunging their slightly opened bill into the sand at frequent intervals as they run, like an animated sewing machine, to search for prey. When a prey item is felt, the bill tip closes on it and extracts it from the sand. Sanderlings foraging like this leave characteristic series of probe holes.

When foraging visually, a Sanderling moves just as rapidly and must have superb vision to see the tiny prey items that it seeks. Many amphipod crustaceans are taken this way, but some days they seem to be hunting thin worms, polychaetes of the family Capitellidae. This prey item is not mentioned in the most recent account of Sanderling natural history, yet all birds appeared to be feeding on them on a recent February visit to Long Beach, Washington.

A bird would move rapidly along, then suddenly stop and grab an incredibly thin worm and pull it quickly from the substrate. It would swallow it in a few gulps, sometimes running off while doing so. Birds were crisscrossing in front of us constantly, presumably spaced out to avoid direct competition for a single prey item. Hundreds of worms were being consumed, but I am sure there were many more where those came from.

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About the Slater Museum

Our goals are to preserve and provide a collection of specimens to be used for research and education. Located in Tacoma, Washington, the Slater Museum is one of the region's significant repositories for bird, mammal, reptile, amphibian and plant specimens from the Pacific Northwest. In addition, we strive to educate the local community about nature and about the value of museums.